This invention relates to energy cells for horological devices, especially electric wristwatches. More particularly, the invention relates to an improved energy cell configuration which permits the largest possible cell volume and optimizes utilization of space in an electric watch.
Small primary energy cells used, for example, in watches and hearing aids are generally of a circular cross section and sometimes called "button" cells because of their shape and size. Such cells are generally alkaline cells and a typical cell uses a zinc amalgam anode, a mercuric oxide cathode, and an alkaline electrolyte such as potassium hydroxide.
An example of an improvement in such a cell is seen in U.S. Pat. No. 3,708,343 issued Jan. 2, 1973 to Walsh and assigned to the present assignee. That patent, which is incorporated herein by reference, employed an auxiliary insulating cap to provide an additional insulating seal over portions of the top anode cap.
It is known to construct a battery comprised of a plurality of cells, wherein individual cells have a particular non-circular shape in order to fit a container or wrapper. Such cells are suggested in British Pat. No. 23,238 (A.D. 1914) to Beaumont and French Pat. No. 787,005 to La Pile Leclanche Belge (1935). These shapes are dictated by requirements of nesting in a group of cells.
Small round or button cells have been used in electric watches for some time, but the circular shape does not permit the maximum utilization of space inside a watch. Particularly in a watch having a substantially circular movement assembly and a "center wheel" rotatably mounted in the watch, the conventional button configuration of energy cell is very wasteful of space and necessitates the diameter of the watch being greater than necessary because of the poor utilization of space by the energy cell.
Accordingly, one object of the present invention is to provide an improved configuration for an energy cell especially adapted for an electric watch.